Low
d.09 on Vaillant Home System

Your boiler is simply displaying the target temperature being requested by your external thermostat, rather than indicating a breakdown or internal fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Heating flow set target temperature that is set on the eBUS room thermostat: Current value

From this model's manual
Verified against the Vaillant Home System installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check your room thermostat or smart phone app to see what temperature is currently requested.Adjust the thermostat settings up or down to see if the value on the boiler display changes accordingly.Ensure the thermostat has working batteries if it is a wireless model.

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